Simplify the following expression: $7\sqrt{125}$.
Solution: First, try to factor a perfect square out of the radical. $= 7\sqrt{125}$ $= 7\sqrt{25 \cdot 5}$ Separate the radical and simplify. $= 7\sqrt{25} \cdot \sqrt{5}$ $= 7 \cdot 5 \cdot \sqrt{5}$ $= 35\sqrt{5}$